1. Field of the Invention
The present invention relates in general to control system for an automatic washing machine and, more particularly, to a motor speed detecting device for precisely detecting and controlling the motor speed of the washing machine by means of speed detecting means having a Hall effect linear sensor mounted to an end of a motor shaft, thus to effectively wash different kinds of laundry in accordance with different washing modes agreeable to intrinsic characteristics of the different kinds of laundry and to improve washing effect of the washing machine.
2. Description of the Prior Art
With reference to FIG. 1, there is shown a typical washing machine. In the drawing, the reference numeral 20 denotes a washing tub placed in a washer housing 10, which tub 20 will contain therein washing water along with laundry to be washed. Horizontally placed inside the housing 10 under the washing tub 20 is a support plate 30 for supporting the washing tub 20. The edge of the support plate 30 is fixed to the interior surface of the housing 10. A clutch unit 40 which is mounted to the bottom surface of the support plate 30 has a clutch shaft 50. The top section of the clutch shaft 50, which clutch shaft 50 penetrates the clutch unit 40, in turn penetrates a shaft hole 50' of the center of the support plate 30 and extends into the interior of the washing tub 20. In order to agitate the laundry in the washing tub 20 during washing operation, an agitator 60 is coupled to the top end of the clutch shaft 50 in the washing tub 20. Meanwhile, the bottom end of the clutch shaft 50 is provided with a clutch pulley 70.
Mounted to the bottom surface of the support plate 30 beside the clutch unit 40 is a drive motor unit 80 for generating rotating force, which force will be transmitted to the agitator 60 so as to rotate the agitator 60. The top of the motor unit 80 is fixed to the bottom surface of the support plate 30. The motor unit 80 has an output shaft 90, which shaft 90 extends downward from the unit 80 and has a motor pulley 100 at its bottom end. The motor pulley 100 is connected to and cooperates with the clutch pulley 70 by means of a V-belt 110.
The top of the housing 10 is covered with a top cover 120, which cover 120 has a size sufficiently covering the top of the washing tub 20. In order to supply water for the washing tub 20, a water supply unit 130 is provided on the top section of the housing 10. The washing machine further includes a drain unit 140 for draining water from the washing tub 20 after washing operation, which drain unit 140 is provided in a lower side section of the housing 10 and has a predetermined length of drain hose 150.
In washing operation of the above washing machine, the motor unit 80 is applied with electric power and outputs the rotating force through its output shaft 90. The rotating force of the motor 80 in turn is transmitted to the clutch unit 40 by way of the motor pulley 100, the V-belt 110 and the clutch pulley 70 in turn. Upon reception of rotating force of the motor 80, the clutch unit 40 transmits the rotating force to the agitator 60 while alternately changing the direction of the rotating force into clockwise direction and into counterclockwise direction in accordance with a control signal applied from a microcomputer (not shown) of the washing machine. Therefore, the agitator 60 is periodically alternately rotated in opposed directions, thus to agitate the laundry in the washing tub 20 and to promote frictional contact of the laundry with the washing tub 20 as well as with the washing water.
As described above, the washing operation of the typical washing machine is carried out by clutching motion of the clutch unit alternately changing the direction of the rotating force of the motor into clockwise direction and into counterclockwise direction in accordance with control signal from the microcomputer. However, the above washing machine can not effectively control the motor speed, thus to fail in letting the motor speed be agreeable to intrinsic characteristics of different kinds of laundry. Therefore, the washing machine has a problem that it can not achieve desired washing effect when washing a specified laundry which needs to be specifically washed at a controlled motor speed.